Basketball is hardly mental, few sports are. Basketball is played off of instincts.
"He's got great basketball instincts" is a mental quality...because its still split second DECISIONS...also, it comes from hours and hours and hours of repitition and experience so that the decisions become automatic, like the differenc between someone who knows the offense and someone new who doesn't.
Also - floor spacing, defensive adjustments, offensive adjustments, timing in your execution, understanding of your teammates tendencies, understanding your opponents tendencies, clock management, possession management, game strategy are all mental and factors commonly discussed as basketball IQ
Will to win, confidence, aggressiveness, giving multiple effort, staying poised, not being rattled, not quitting, competing till the final buzzer sounds are also all mental "intangibles" but real nonetheless.
Much of the laker offensive problem this year is their poor floor spacing...much of San Antonio's brilliant offense this year is their incredible floor spacing...that's just one item on the long list above.
Basketball is almost completely 90% mental. It's why similarly talented players don't compete with similar intensity, or make similarly good decisions, why removing one or two bad "character" or "low iq" guys from a team makes the team much better. I can go on and on but it is what it is.